In manufacturing environments, it is often desirable to identify articles of manufacture by reading a code imprinted or otherwise present on the article. It is also often desirable to inspect articles of manufacture for quality control purposes. In this manner, articles that are out-of-date, or that have defects, flaws and the like may then be rejected or otherwise distinguished from the lot of articles undergoing such inspection.
For example, in the bottling industry, returnable bottles that are over a certain age limit (such as those over four years old) may be automatically rejected regardless of their apparent condition. Similarly, bottles may be automatically rejected if a significant number of their lot have previously been detected as flawed.
Moreover, it is often desirable to inspect the physical condition of both glass and plastic bottles, such as inspecting for the presence of foreign matter or for cracks in the bottle. In the case of returnable plastic bottles, each time the bottles are handled, washed, pressurized, depressurized, and so on, the bottles are subjected to stress which may cause cracks to form thereon, particularly on their bottom portion.
One such bottle inspection system, which is directed to detecting foreign matter within a bottle, employs a camera above the bottle operating in conjunction with a light source below the bottle. However, such a system does not provide reliable data for analyzing the stress cracks on the bottom of the bottle. For example, with this typical arrangement, newer bottles create a significant amount of glare which makes it difficult to detect stress cracking on the bottles. Moreover, such data is even more unreliable if water droplets are present in the area being analyzed. In short, these typical bottle inspection systems are unreliable and therefore unsuitable for performing proper stress cracking inspections.
However, properly inspecting the condition of the bottles for defects such as cracks and other flaws and reading the codes on the bottles is a time consuming and expensive process. Since returned bottles are randomly mixed and since each bottle generally experiences an unpredictably different amount of stress during its useful life, each bottle must be individually inspected to achieve any measure of assurance that the bottle is acceptable for refilling.
Ordinarily, at the time of manufacturing each bottle receives an ink or laser-imprinted coded label i.e., code string, that is used to identify the bottle during its useful life. In this manner, information regarding the bottle's date of manufacture, place of manufacture, lot number, and the like may be imprinted thereon. In the case of returnable plastic bottles, the coded label is often imprinted on the lower portion of the bottle perpendicular to its longitudinal axis. However, it is difficult to consistently position these coded labels on the bottles. For example, as the bottles move along a conveyer belt, they often become slanted upwards or downwards, i.e., they often become slightly nonperpendicular to the longitudinal axis of the bottle. During the application of the code string, when a bottle is slightly skewed, the code string is necessarily imprinted thereon in a similarly skewed manner.
Moreover, the bottles are often randomly rotated about their longitudinal axes both initially during the labeling process and later during subsequent handling. When attempting to read the code at a later time, such as when the bottles are placed upon a conveyor belt to be ultimately filled, it is often difficult to locate the positions of the labels while they are moving. This is particularly true when the conveyor belt is at maximum capacity, i.e., when there is essentially no gap between the bottles on the conveyor belt.
Adding to the complexity of locating and reading the code is the fact that the bottles are continuously moving and it is usually undesirable to reduce the throughput of the system by reducing the average speed of the bottles or the conveyor belt to facilitate the reading and inspection of the articles. Likewise, inspection of the bottles is also a difficult procedure due to their continuous movement.